I still need float-rigging info [Archive]

Lynn Matteson

11-14-2014, 06:11 PM

That's great information coming from you, as I regard your opinion highly...from what I've seen here and in speaking to you personally....back in about 2005 or so at the seaplane base at Oshkosh.

You won't remember this, Paul, but I spoke with you about flying a short-wing Kitfox with a Jabiru 85 hp engine and you said that it would take a long-wing and probably 100 hp to get off the water succesfully. At that time, I was just building the plane, and pretty much gave up on the float idea back then.

By now, I've got 1595 hours on me and the plane, and have become bored with just flying around the patch (and around the country, from California to New York with this plane) and I needed a project to get my juices flowing again. I had just finished helping restore John Cuny's Republic Seabee....Grand Champion Seaplane this year....for the past 2 years, and I needed a project of my own. Over the past years of flying with the 2200 Jabiru, I have built tuned exhaust pipes for it, a large-plenum intake manifold with long tuned intake runners, and an Electroair ignition system. With all these mods, I got to thinking that maybe I might be getting close to that magic 100 hp that you said would be necessary for float operation. So that's the background behind this latest project of mine. It would be great to get the rigging such that it would be adjustable. My local mentor, Brian Vanwagnen, has already suggested that I do away with the "X" braces that Zenair supplies, which are cable, and I've started to make these from SS rod, 1/4" diameter. And I have built the floats using solid, driven rivets in place of the "pop" rivets that they provide.

Probably email would be the way to go, unless the moderators feel that your provided information would be of benefit to others, and in that case, posting here would be fine.

Lynn (lynnmatt@jps.net)

Av8r3400

11-14-2014, 09:07 PM

Lynn and Paul, If you don't mind sharing, I think this would be good information to share openly with the Kitfox Community…

Please post any details here.

av8rps

11-15-2014, 07:14 AM

I remember talking with you.

By chance have you ever done a thrust test on your plane? Just curious, as that is even more important than the actual horsepower for flying floats.

And I may have changed my opinion some about the short wing. A standard Just Highlander makes for a really good seaplane, yet the wing area is less than a standard Kitfox wing. So I'm thinking it is probably more equivalent to a Kitfox Speedster's wing area. If true, then the shorter Kitfox wing should work just fine. At least that's my current take on things right now :)

I'll try to post what I come up with here on the forum rather than an email since the group is interested.

Lynn Matteson

11-15-2014, 12:27 PM

Your take on the wing area is good news, as I haven't wanted to re-build the wings out to standard Kitfox size. I have the sawed-off (by a previous owner of the [then] unfinished plane) sections, but being as I have installed anchor nuts for mounting the wing tips, it would be a bummer to have to do that job over again.

I haven't done a thrust test, but I've often thought about it. Being a "numbers" kind of guy, I have often wondered what I was producing hp-wise, but never bought the pull tester that (for one) Valley Engineering sells. Maybe I will look into that, as I have got the floats just about as far as I can go with them, building-wise, and running out of things to do before it becomes time to strap on the skis...(for the plane, not for my feet). : )

Lynn

av8rps

11-16-2014, 07:09 AM

Lynn,

Don't go out and buy a tester on my account. I was just curious what the 2200 modified would do. I doubt you would have gone so far as to build a set of amphib floats if you didn't think they would work.

It's actually pretty simple; if you think your jabiru speedster will compare at all with a rotax speedster performance wise, it's probably going to work on floats similarly. So we just need to get those floats on to figure it out.

The biggest question I have about this is if your existing prop will have enough thrust being that it is so short? It would be interesting to talk with either jabiru or lonnie prince to see if you could run a longer prop. I've heard of guys with jabs running 64 and 68 inch props with success. But again, that's just my idea. Your existing prop might be just fine.

Paul

kmach

11-16-2014, 07:31 AM

I don't know if you have spoken with or are aware of these people - Harbour Sport Aviation , I ran across their website last winter when searching the net for float options. They might be able to help you out .

Paul Z

11-16-2014, 07:53 PM

http://www.homebuiltairplanes.com/forums/bush-float-flying/2699-float-installation.html

http://www.supercub.org/forum/showthread.php?36366-Rigging-floats

http://www.zenairfloats.com/rigging.html

av8rps

11-19-2014, 03:22 PM

*** NOTE - UPDATED WITH CORRECTIONS ******

Sorry if this becomes redundant, but I haven't heard a word of response to a month-ago request for float-rigging info for my Zenair floats on a model IV. And I can't seem to get off a private message either. I know you float-fliers are out there, and I'm anxious to join the party. : )

Lynn Matteson

Ok Lynn, I have some info for you. I did some calculations using a variety of float install information I've aquired over the years, and then called a few people that I consider to be float experts to see what they thought about how to best float a Jab 2200 Speedster? The good news is that we all came up with approximately the same numbers. The bad news is that I can't tell you exactly how we came up with that, as we all used different methods to arrive at our numbers :confused: . But after talking about what would be best for your situation we all agreed that the best thing to do is to use experience rather than formulas. Many seem to think that float installation is a science, but the reality is that it's more like an art. So in the end the numbers we decided to use are based on our collective experience more than what you might find in some textbook. But we're confident that it's more likely to help you than if you were left to do it by the book.

But I do have to make this disclaimer; None of us are formally trained on any of this. We're just guys that have been flying these kind of floatplanes for a lot of years, and have learned mostly through our own trial and error. So don't be surprised if you find that you may have to tweak things a bit after you've installed the floats on your airplane. With homebuilts since no two are alike you almost always have to do some trial and error before you get it right. And while I'm pretty confident we can get you 85-90% accurate to where your floats need to be, it's likely that you may need to tweak the throat angle and/or step placement if you want to extract the top performance from your new floatplane. And if by some stroke of dumb luck our numbers work well without any tweaking, then you can just consider that a bonus you get to enjoy from all of our years of fiddling :)

So let's cut to the chase;

- First, set your spreader bars so that the floats are no more than 8 ft wide at the widest part. Typically that means that if you drew a centerline down each float lengthwise, from the center of each float (with Zenairs that would be the channel that you walk on), that measurement should be 6 ft. Our experience has shown that a lot of people put the floats too far apart, reducing their off-the-water performance of the float. Most people don't know this, but the bow wave coming off the front of each float helps to hydrodynamically lift the other float next to it in the initial part of the takeoff run.

- Second, set the floats up for about a 22 inch height from the top deck of the float to the bottom longeron on your Kitfox. That should give you enough prop clearance, while still benefitting from the use of ground effect to help make the wing lift sooner. You will notice when looking at most of Zenairs float install pictures that they tend to mount their floats further away from the airplane than what I'm telling you. That's not to say what they're doing doesn't work. But if the aircraft is kept closer to the float it typically results in having the wing closer to the water, which makes better use of ground effect (or should I say water effect?). The theory is simple, as the aircraft moves forward the air becomes slightly compressed under the wing, which helps to create lift sooner. Or at least that's what some of us believe ;) (plus, sitting lower on the floats also helps with stability on the water)

- Third, level the Kitfox using the bottom door frame tube (this is very important). Then locate the most aft (rearward) center of gravity for your Kitfox, and run a plumb bob down from that area of wing to the floor.

- Fourth, slide the floats under the aircraft until you have located the step 3 to 5 inches aft of the rearward Center of Gravity range for your Kitfox (3-5 inches from where the plumb line is hanging). On my Kitfox equipped with Aerocet floats (which handles and performs marvelously), that positions the step directly below the middle of the 3rd (from the front) landing gear attach bracket (see the photo I attached of the float rigging dimensions for my Kitfox to see what I am describing. But note that the 23 inch measurement I am showing in the picture was done only so you could have an easy way to see EXACTLY where my step is located). Your step location should be somewhere near where mine is in the picture. And you probably will find it even further aft as the location of the step on my Kitfox is as far forward as you would want a set of Zenairs. If you put it further forward you are likely to have water handling issues (e.g. porpoising), and too much forward CG.

The Zenair amphib is about 2 ft longer than my Aerocet amphib, so when the Zenair is installed the bows with all the nosegear weight is much farther out in front of the airplane than mine, and likely will cause the aircraft CG to move quite a bit forward. So it is possible that you might need to move the float even further back than the 3-5 inches. The good thing is that having to move the step back because the float is long doesn't do much to affect water handling. The worse it does is (maybe) extend your water run for takeoff.

But have the step too far forward and you can cause all kinds of weird, and even scary water handling issues.

- Fifth, set the float angle. On an aircraft with a high power to weight ratio you can get away with just a 2 to 3 degree (tail low) angle on floats. But for most normal aircraft that number is more like 4 to 6 degrees. In the case of your Kitfox I would recomment going with a 4 to 5 degree angle (using the top of the float and the bottom of the door frame) as the Kitfox wing does generate a lot of lift for its size, and your overall wing loading is still relatively low.

The last two photos attached are just there to show you how the float should look when the airplane is at high speed on the step. Commonly a floatplane will ride on only about 4 inches of the float, the area just ahead of the step (also known as "The sweet spot"). It may look as though the back of the float is skimming too, but it is essentially that small 4 inch area ahead of the step doing all the work. That's why it is ultra critical to have the step in the right location.

One last suggestion is to study the photos of my Kitfox closely, as even though I have Aerocet amphibs and you have Zenairs, the concept is the same. So if you can just make a few minor changes to your rigging as explained above, it's likely you will get great enjoyment from your new Kitfox floatplane.

I will follow up this post with some more pics that I also feel might help you.

Paul

(please forgive my late editing - I had a computer crash earlier)

Lynn Matteson

11-19-2014, 06:14 PM

Thanks VERY much for that info, Paul. Just to give you a bit of feedback, I had set my floats up exactly to the 6-foot centerline separation that you suggested, and because my floats are 24" wide, the max of 8 foot that you mention is adhered to. I went with the 6-foot centerline wheel separation that my Grove landing gear gave me, as that looked "about right for float separation." (solid engineering presumption on my part, eh?)

Next, I had rigged up a mock Kitfox lower longeron "frame" and had this spaced 18 inches above the float walkway. I had originally figured that I had to keep the overall height of the tail fin under 120" due to the height of my hangar door. Your dimensions will fit within this parameter. I'll just raise the lower longeron on my mockup. This mockup is just to give me an idea of what the struts and diagonals will look like and allow me start some of the cutting on those parts without having to actually ground the plane so soon. I wouldn't actually build to this mockup, I will just use it for getting the bottoms of the struts and diagonals cut to shape, leaving adequate length for the tops to be cut when the plane is actually hanging over the floats.

Lynn

av8rps

11-19-2014, 07:25 PM

Thanks VERY much for that info, Paul. Just to give you a bit of feedback, I had set my floats up exactly to the 6-foot centerline separation that you suggested, and because my floats are 24" wide, the max of 8 foot that you mention is adhered to...

Lynn,

I had a computer crash (and a brain crash :eek:) after a bunch of interruptions while trying to put this whole thing together for you. So please make sure to go back and read all that I just reposted. It will probably make more sense than the earlier gobbledy gook I wrote.

I like the idea of your rigging mock up. I'm not that smart, I just crawl around under the airplane while it hangs mid air from a chain while I cut struts and cables :confused: (see pic below and note wife's comment "Are you sure this is safe?)

Your 18 inch spacing between the fuselage and top of float would probably be ok because you aren't running a long prop.

But also remember that whatever throat angle you use will lower or raise the tail accordingly. And it's amazing what an inch or two off a strut can do to tail height. The original rigging I got with my used Aerocets were modified for a VW powered Kitfox , so it had a HUGE throat angle. After I figured out what I needed for struts and I got them installed the tail came up a about a foot and a half! I'm lucky I have a tall hangar...

(of course a guy can always build a cart or two to go under the nosewheels to keep the tail down when in the hangar)

av8rps

11-19-2014, 08:25 PM

I put at the end of this post a random bunch of old photos I had saved of Kitfoxes with Zenair or Czech floats installed. I thought if you hadn't already seen them you might like to. As we all know when it comes to building things, sometimes a picture can be worth a thousand words...

(Incidentally, the blue, red, and white Kitfox IV on white Czech amphibs is a short wing Speedster version as I recall...FYI )

In addition, just below this post you should find a mechanical drawing of my Aerocet float details with dimensions. But more importantly it shows my full scale drawing of the fuselage attach brackets you will probably need for installing your floats on your Kitfox. You might still be able to buy those fittings from John or Deb at Kitfox? But if not you can hopefully make your own from the drawings on that sheet. I traced them full scale and then scanned them into digital, so I'm thinking if you print that page on an 8 1/2 x 11 piece of paper, you should probably end up with a full size template. And if not at least the fuselage attach fitting concept is there for you.

But if you do end up making your own, I would recommend making the fittings longer (per the hashed lines I added). That way if you need to you can adjust your float rigging up or down without having to buy all new (expensive) strut material.

Paul

Lynn Matteson

11-21-2014, 07:17 AM

I put at the end of this post a random bunch of old photos I had saved of Kitfoxes with Zenair or Czech floats installed....Paul

Thanks for the updates, Paul. I haven't re-read the original posting (with edits) nor all of the latest, but just skimmed it enough to make a reply. The one thing about rigging that Zenair DOES make available are machined fittings that fit the Kitfox IV factory-welded brackets. I already have these fittings and all the strut and diagonal brace material, and of course the plane has the 4-on-each-side float/ski brackets. Yesterday morning, after thinking of how to make the rigging somewhat adjustable, I laid an aluminum bar across the pickup tubes on one of my floats...fore and aft...to check on the feasibility of making the throat adjustable. I leveled the float so this bar was reading "zero" on a digital level. Then I placed a 1/2" shim under one end of the bar....the dig. scale read 0.5 deg. Then I removed the 1/2" shim and used a 1.5" shim (2x4) and the reading was 1.5 degrees. Swapping the shims to the other end, one at a time, and the reading were the same. In short, as luck would have it, whatever the thickness of the shim is in inches, adjusts the reading a similar number of degrees. So if I were to use, say, a 1" shim under each of the four rigging blocks that bolt to the spreader bars, then set the plane-to-float (throat angle) angle at say, 4 degrees, fly it, and if an adjustment were necessary, I could remove the front 1" shims, and the throat would close up 1 degree to 3 degrees, or remove just the rear shims, and the throat angle would open to become 5 degrees. Or, if the plane flew well at the original setting, I could remove all four shims, and still be at the 4 degrees of the original setup. Now, is this what others have done to have some adjustability, or am I all wet (no pun intended) on this theory? Using shims judiciously under what Zenair calls the "pickup fitting" which is shaped like a pillow block and to which all the fittings are attached, raises or lowers the entire rigging package...struts, diagonals, x-wires, and airplane....at once, and no changing of the struts or diagonals is needed. So, in my thinking, I can easily change the throat angle, but it's the placemant of the step in regards to the C of G that would involve drastic changes of strut/diagonal tubing length if that original step/CG placement were not made right to begin with.
Your thoughts?

Lynn

av8rps

11-21-2014, 09:33 AM

Lynn,

Typically people use extended float fittings at both ends (float and fuselage) so that you can move it up and down in the other bolt holes to adjust it wherever needed. But the way you are describing yours with using shims, I can't see why that wouldn't work just as well.

And yes, I agree it is much more difficult to be able to adjust the step location. I've seen people use a c-channel mounted upside down to the top of the float (usually attached to the area where the spreader bars are) so the struts could be moved to different bolt holes in the c-channel, allowing the float to be moved fore and aft by just moving the strut fittings in the bolt holes. If you can figure out a way to do that even temporarily until you are ok with how your airplane performs, that could save you a lot of time and frustration (and probably money because you won't need to cut up so much strut material). Once you know you are happy with how the floats perform, you can always make a permanent fitting for attachment.

Half the battle with installing floats is understanding what you are trying to actually accomplish. And from what I'm hearing from you, you are most definitely on the right track :)

Paul

Lynn Matteson

11-21-2014, 11:54 AM

Lynn,

Typically people use extended float fittings at both ends (float and fuselage) so that you can move it up and down in the other bolt holes to adjust it wherever needed...

Thank, Paul....I hadn't thought of the C-channel idea for fore-to-aft placement, but that's a good idea. I might even be able to incorporate the shimming-for-throat-angle method into the C-channel idea, and have a more or less universal temporary flyable mount. This is getting exciting!

Lynn

Lynn Matteson

11-21-2014, 03:18 PM

Paul-
I have a question regarding that blue, red, and white Kitfox IV....it is the only one of the planes pictured that has the diagonal brace starting from the rear fuselage bracket and going forward and down. I have been told that the diagonal brace (on float-equipped planes)will start at the fuselage directly above where the original landing gear was mounted...or near where the original main wheel was. So, if that is true, that would make all the other pictures of Kitfoxes (that you posted) appear to have been originally tailwheel planes, and the blue, red, and white one would have been a tricycle gear plane originally? Just curious...

Lynn

av8rps

11-22-2014, 08:24 AM

Lynn,

I don't think that installation has anything to do with being a taildragger or a trike gear setup.

I'm guessing the reason for that is because those floats have the spreader bars closer together than most floats. A lot of builders as well as manufacturers don't really know what they are doing when putting floats together, so they put spreader bars too far back, too far forward, too close together, etc, etc.. if you compare the blue airplane to the others, you will notice there is a lot more float forward of the the front speader bar, besides the rear spreader attach being moved forward causing that rear strut to be more vertical. So something is different with those floats than most. At one point I do know the Czech's were building a 1250 that moved the step 6 or 8 inches back to offer more forward buoyancy for the Rans S7 guys, and I know the first sets did not have the spreader bars moved ahead to match the new step location. So I'm guessing those might be a set of those floats?

The Czechs did the same thing on their first set of their CZ 1300 amphibs. They made them initially for a specific airplane that had really closely spaced attach fittings that also were way far forward. They essentially couldn't give those floats away for install on other airplanes until Ken from Harbor sport aviation modified them and redesigned the landing gear so they could easily be mounted and used on other airplanes like the Rans, Kitfox, Highlander, etc. Ironically, after the spreaders and gear were fixed, they became one of the nicest floats out there.

av8rps

10-09-2015, 02:18 PM

Hey Lynn, are you out there?

I never heard back to see how your float installation turned out? I figured by now (knowing how commited you were to making a Jab powered Speedster work on floats) that you must have it all figured out or you would have recontacted me.

Hopefully you are having so much fun on your floats that you didn't have time to write :) but now that float season is ending I'm hoping you may have some time to let us know your results.

Paul

DesertFox4

10-09-2015, 07:30 PM

Lynn hasn't logged in since 2-1-15. Hope he is ok.

av8rps

10-10-2015, 06:08 AM

Thanks. I'll see if I can track him down through some mutual friends.

Lynn Matteson

10-11-2015, 06:51 AM

Thanks. I'll see if I can track him down through some mutual friends.

Hi Paul

Good to hear from you. I tried to answer last night with a text from my cell phone, but it apparently didn't go through. Rather than go into a lengthy discourse of what has happened with the floats so far, I'll send this and see if that works. If it does, get ready for a lengthy tale of some success and a lots of woe.

Lynn

av8rps

10-11-2015, 06:52 PM

Hey Lynn, nice to hear from you!

I'd love to hear your success and your woes with floating your Fox, and I'm sure others here on the forum would too. So please, by all means share with us your experiences with putting amphib floats on your Kitfox 4 Speedster.

Paul

Lynn Matteson

10-12-2015, 07:47 AM

Hey Lynn, nice to hear from you!

I'd love to hear your success and your woes with floating your Fox...

After I got the floats rigged (pretty much to your suggestions, Paul), I tried taxiing, and the plane wouldn't respond correctly to input from brake applications...this is an anphib, as you recall. It turns out that I had crossed up the brake lines during the installation, so I swapped the lines where they crossed and this small problem went away...duh!

We got all the weights recorded, balance was within specs, and my flight instructor took it up for a flight...perfect...no handling issues. He took it to the lake, made a couple of landings, then I got in with him for a test flight, and a lesson. With two of us aboard...me 165 lbs, him 235...the plane took forever....45 seconds plus...to lift off. Next we tried getting on step, lifting a float and popping it off the water. This worked, but he suggested that the step needed to go further aft, as he could feel the aft of the floats being "snatched" down upon landing, and that the sweet spot was too hard to hold when trying to get on step. We tried more landings and takeoffs, but it was always the same story....long takeoff runs.

He suggested that because of the short wings, lift was suffering, so I told him that I could add the previously cut off (prior to my buying the incomplete plane) wing section back onto the plane.
That job kept me busy for a couple of weeks, and when I had that little chore done, I tried a flight...not much better, I felt, but hard to compare with previous flights from my field because of the long wet Spring, and the soggy grass runway, now dried out and comparing those conditions with a now-longer wing and now dry conditions.

During the next few weeks, I got intermittent training in his J-3 on straight Edo floats, and was getting more comfortable with this whole different aspect of float-flying, but not ready to solo yet. This was partly due to the backwards layout of the Cub....tach reads backwards, controls are in opposite hands, can't see the carb heat knob, water rudder lift handle is to the side and slightly behind me...all hard for this 78-year old adjust to. : )

All that, and his available time is short, because of his job flying for a major airline, and domestic duties, none of which I have, so the frustration level on my part is raising.

A couple of times he would have me landing at his place, and would distract me with talk of something or the other and I'd be on final with the wheels still up...exactly what he wanted to see. So he'd have me go around, naturally, and by now I figured that a checklist would be handy, and also for me to call for a "sterile cockpit" which shut him up. :) Don't get me wrong....he's just trying to keep me safe...and we get along just fine. I also work on planes for him in my spare time at his place.

So eventually he flies it to a hard-surfaced airport near here, (I drive) and do multiple landings on that smooth surface and he finally ok's me to fly solo after he's convinced that I can call out all the checklist items....carb heat, mixture, landing gear position, rpm, water rudder position, etc. I do 3-4 solo landings and he ok's me to fly it home solo to my place....finally, after 5 weeks of installing the floats, having it flown for tests, and flying it with my instructor, I was released to fly it home solo and park it in my own hanger. Now I can fly it by myself again...from and to land only, mind you...but at least I can fly it alone again. And now is when I can get into trouble ALL by myself...and I do!

That's enough for this segment, I'll continue later or tomorrow...Oshkosh experience, coming up.

Lynn

kmach

10-12-2015, 08:00 AM

Hi, great story.

Did you end up moving the step aft some ?

I have a pipe dream of amphibs on my outback series 5, so all these stories , life lessons are very interesting!

av8rps

10-12-2015, 03:59 PM

Hey Lynn, can you type faster? ;)

I'm on the edge of my seat waiting to hear the rest!

Paul

Lynn Matteson

10-13-2015, 03:23 AM

Landing gear woes

Now that I've got the plane back in my hangar, I can fly it to local fly-ins, breakfasts, etc., but with a warning from Brian (my flight instructor, mentor, and good friend) that these floats are not the strongest he's ever seen, and that the landing gear is the weak point. I shouldn't be considering them to be as strong as the Grove landing gear that I built the plane with, and I ought to be operating them on hard/smooth runways whenever possible....in other words, cut out some of the turf activity. Well, that's hard to do when my place is turf, and so is his, and so are most of the places I frequent. So I kinda let this advice fall on deaf ears, which mine nearly are, and this will bite me in the ass later on....

So now I've modified my plane, after I've flown it for over 1600 hours and to both coasts of the US, into something that I can't fly to all the places that I used to, can't fly it into lakes, etc., because the training is dependent on Brian's time being available, and I'm getting frustrated.

I should point out here that when I built and installed the floats, that I installed a couple of pressure gauges to show the pressure in the gear retract system...a pressure gauge for the "up" direction, and another for the "down" direction. Because I can't see the actual position of the wheels, I operate the switch (operation is electrical/hydraulic pump) in the chosen direction until I see the pressure gauge max out, telling me that the work is done....all four cylinders are at their maximum extension or retraction, whichever the case may be, and I can release the switch. Right from the start of the project, I had built mechanical indicators for the front wheels to show up or down, but nothing yet for the main wheels. I was relying on the pressure gauges to show position indication of the mains, either up or down...another ass-biter coming up.

Lynn

Lynn Matteson

10-13-2015, 03:26 AM

Hey Lynn, can you type faster? ;)

I'm on the edge of my seat waiting to hear the rest!

Paul

I can type faster, but the squirrels in the modem are complaining.

Lynn;)

Lynn Matteson

10-13-2015, 06:05 AM

Landing gear woes solved?

Somewhere along the way, Brian suggested that as old as I am, and having flown only one plane (not true, I've flown about six different planes, but no solos in them) that I should look into getting a device to remind me to check gear location. I figured that the gear position is the only thing different about flying this plane now as opposed to wheels only flying. He pointed out: "Isn't your life worth $600?" (approx. cost of a gear position reminder device that calls out wheels down for runway landing, or wheels up for water landing)
I guessed that it was, and ordered one...it'd give me something to do while waiting for the next lesson. So I got the device from Spruce, and it needed info from the gear telling it where the wheels actually were....position switches. So I set about building a small switchbox containing two microswitches, one that would close (complete the circuit to ground) when wheels were up, and one that would close when wheels were down, and I wired them into the plane. I then built a small subpanel ( running out of room on the main instrument panel) and mounted a green light (runway landing) and a blue light (water landing). This worked great! Now instead of watching for the pressure gauges to indicate when the wheels were at their end positions, I had these really cool lights that came on to tell me the same thing...or so I thought.

I got this panel mounted on the plane the day before I left for Oshkosh. Took it up for a flight or two and everything was ginger-peachy. Weather kept me from going until Monday of Oshkosh week, and when I did get going (west from here [southern Michigan], then around Chicago, then north) I had a 10-15 mph headwind until I turned north. I finally got there, stopping once for fuel/**** call, then landed on 27 at OSH, and made the turnoff to head for Seaplane parking. An attendant crossed his arms in front of me and I stopped. "You have smoke coming from your right float" I got out and the right float was dragging on the pavement. A small group had gathered and they lifted the wing while I ran the "'down" switch. The wheel locked into position, I thanked them and taxied off to my eventual parking place.

When I had changed my procedure from watching the gauges max out as an indicator of "locked and loaded", to watching the light come on, I overlooked the fact that the light was indicating that ONE wheel, the left one, (the ONLY one with the switches) was locked, and I still needed to observe the gauge for max pressure...the only true (more on this later) indicator of maximum wheel movement.

More later...gotta go install a bladder tank into a Republic SeaBee.

Lynn

kmach

10-13-2015, 06:48 AM

I enjoy reading your adventure. Thankyou for sharing your experiences

av8rps

10-13-2015, 07:08 AM

I'm still sitting on the edge of my seat...;)

Lynn Matteson

10-14-2015, 06:27 AM

I'm still sitting on the edge of my seat...;)

Hang in there, Paul, more adventure on the way.

Prior to Oshkosh

I left out an important part of this journey into "floatdom"....prior to devising and installing the landing gear position indicator, I had made a flight up to Clare Muni airport for a breakfast (they've got the best cheesy potatoes in the land):) Leaving there...without the benefit of my GPS, which went belly-up some time ago, I saw a freeway which I thought was the N-S one, I followed it, and ended up going NW-SE towards Saginaw and some Class C airports. When I realized this, I made a correction to go south and get out of their territory. I was getting frazzled by now and tired, and wanted to get home.

When I got home, I saw my hangar-mate waiting for me, and, wanting to make a great landing to impress he and his wife, I brought it down the grass runway and made the smoothest touchdown in the history of the world...for a little bit. Then the plane sort of came to a rather quick stop. I thought I had left the line-lock on for the brakes, but then realized I had landed wheels UP! By this time in the flight, all my brain power was used up, and I had finally done what they say all pilots with re-positionable gear will do eventually, and that is make a wheels-up landing. Well, it didn't take me long to accomplish that feat....probably 30 landings into my re-positionable landing gear career, I had my merit badge. We got the floats raised with planks and wood blocks and lowered the gear and in 15 minutes I was able to taxi to the hangar.

It was at this point that I decided to order the annunciator, and build the position indicating switches, because I couldn't trust my brain to remember to check for the proper position of the gear. Then came the incident at Oshkosh, and the realization that even with an audible reminder (which wasn't functional yet) to check gear position, I still needed to have a mechanical device to show where the wheels were...EVERY wheel, not just the one with the microswitches, and the fronts with their mechanical indicators.

So now I had to devise mechanical indicators for both main wheels...what if a wire broke, or a light bulb failed, or the annunciator (if and when I got it functioning) went belly-up?...so I could see proof positive that all wheels were in the proper position for whatever surface I was going to land on, water or land.

I already had the mechanical indicators for the front wheels, and the ones for the mains weren't that hard to devise, so I set about building them. On the Zenair floats, the mains go down and are locked in place by an over-center mechanism, and I used this feature to make my indicators such that as the links go over center, the indicators are actuated, and this can be seen from the cabin via a rod that sticks up through the skin of the top of the float. So now I had all four wheels showing their positions by mechanical means, as well as the pressure gauges to show when the actuating cylinders were at their extreme positions.

Early on in this business of trying to make a fool-proof method of knowing where the wheels were, I had thought of the pressure-indicating method of wheel position as the end-all in knowing where they were....but what if a log were to become jammed between the mechanism and the float? In this case the gauge would show high pressure, but the cylinder would not have moved the mechanism the entire way to either up or down, and I wouldn't know this and would land with one wheel not in the proper position. So that is why I went with the mechanical position indicators. Now when I land, I operate the up or the down switch, watch the pressure gauge for maximum deflection, then observe the wheel-position indicators for proper position for the intended surface. When I get the annunciator working, I'll have that to remind me that I'm going to land on whatever surface the wheels are presently positioned for, and if my brain is working, the landings will be made with the wheels positioned correctly. Now if I can get some more training, maybe I can actually use these things for what they were intended...landing on water.

Next up...fixing the damage from the Oshkosh incident.

Lynn

avidflyer

10-14-2015, 07:58 AM

Lynn, your series of messages reminds me of the 'Cloud Dancer's Alaskan Chronicles' series on the Super Cub dot org website. Hope yours has a happy ending like most of his do. I'm waiting for the next installment. Jim Chuk

Av8r3400

10-14-2015, 04:35 PM

What about a simple pair of mirrors on the jury struts? :confused:

rv9ralph

10-14-2015, 09:20 PM

Mirrors is what I was thinking. I love following the thought process and the execution of a possible solution. It is a learning experience for us all.

Another visual check tool.... wireless back-up camera. Available at auto parts for$50-70. Mount camera in a location low enough to see the wheels when down... or not see them when up.

Ralph

Lynn Matteson

10-15-2015, 07:02 AM

The mirrors have been suggested, but when you get them mounted far enough out that they can be seen, most of them....wide angle...are pretty much useless in trying to determine whether the wheel is really all the way down. My over-center indicator won't indicate until the mechanism is over center and the wheel is locked in place. With a mirror system, the wheel shows up so small that it is impossible to tell if it's REALLY all the way down or not. On the Republic Seabee that we have been working on...ahem, Oshkosh Seaplane Grand Champion, 2014, Sport Aviation, Oct.2014, p.82, thank you very much...:D the mirror for the tailwheel is out on the tip float, and when you try to see if the tailwheel is down, it is SO small as to be useless. He has a light that indicates position, and the mirror is only to verify.
When I came up with the mechanical indicators, it was, in my mind, the easiest solution that was pretty much foolproof, and didn't involve lights, wires, etc.

Now to fixing the Oshkosh damage...

I left Oshkosh two days after getting there...my usuall stay...and flew home
to fix the floats.

After it slid on the belly of the right-side float, there was grinding damage to the keel for about 13" but very little damage to the skin...only about 2" of the skin was ground away. I made an overlapping scarf-type repair to the keel, and overlapped the skin and the step bulkhead with new material.
There was room to reach inside the float to buck rivets, because I had built the floats with pump-out openings in the walkways. I had cut six 3.5" openings into the walkways of each float and installed pumpout cups in the areas of the separate compartments. But I felt more comfortable being able to get both arms inside, so I cut an additional 3.5" x 6" opening into the walkway, and later added a flange and a hinged access cover. Maybe I'll line that compartment with styrofoam and be able to carry ice and beer, eh?

I had taken the floats off the plane to repair the damage, and had the plane flyable the next day after returning fron Osh. Brian called me and I told him I had the floats off and was flying the plane, and he suggested that I come back up to Osh..."you'd probably be the first guy who came in on floats, left and returned to Osh on wheels" I doubted that and opted to not go through the effort...if I had been assured of setting some kind of Guinness Record, I probably would have though.

Anyway, got the damage all fixed, and reinstalled the floats 4 weeks later. It was during this time that I devised the main wheel position indicators, built them and had them in place when the floats went back on. It was also during this time that Brian suggested that the step needed to go further back in relation to the plane. That would have involved making new struts and I was reluctant to just start making new struts, cutting the longer ones down, making new ones, etc., on the notion that this would help the plane off the water. Instead, I decided to build a new set of brackets to allow the plane to move forward...floats back...and these would allow for a movement of 2.75", and if the brackets were flip-flopped, another 2.75" in the same direction. It took almost another 4 weeks of designing and building and installing to get these in place, and in the meantime, I got a few more hours training in the Cub on floats.

While training in the Cub, Brian would have me call out all the moves that I was doing, but as they related to flying the Kitfox. It would go something like: "Kitfox downwind for lake landing....carb heat on...water rudders up...engine speed set...mixture set (Rotec throttle body)...operating gear switch (actually pretending to reach for the switch)...pause...pressure building....pressure maxed out...left float wheels indicate up, right float wheels both up...configured for water landing...."

We would do this time after time, landing on the water, having read the wind direction, and landing accordingly. He would have me do high-speed taxiing, which was ok, but I was not so comfortable doing high-speed turns on the step...it just didn't feel right to me. Also, the Cub tach is a counterclockwise rotation for increasing rpms, and that was WAY different than the digital tach that I ws used to seeing in the 'fox...GRT EIS. The carb heat is located where I couldn't see it, so it was "out of sight, out of mind", as well as the location of the water rudder pull-up handle. All of these little things have a way of frustrating this 78-(79 by the time I get this documented) year-old brain. Along with the little details of flying the Cub dual was the problem of getting the plane into the water and getting ready for a lesson. Brian has a small pond in his backyard which is long enough for the Cub to take off one-up. But because it is a straight-float plane, he has to fly it to a local lake, I drive the car there, wade out, get in, get an hour's worth of work in or so,(about all the stress this old-timer can handle) wade back to the car, while Brian takes the plane home. We then back the tractor and trailer into the water, load the plane aboard, and put the combo into the hangar. Because I don't like to be a burden on others, all this effort to get such short flying time in wears on me....frustrating.

By now, I had the floats moved back the 2.75" and ready for the next lesson. It is amazing how much different it is to get training in ones' own plane, or in any amphib for that matter. I called Brian to meet me at the local turf airport...3NP, Napoleon, MI. He climbs aboard, we lift off the ground...feet are dry, thank you...we make a few landing and takeoffs at a local lake, and he says "It didn't help....move it back to where it was." Thank God I hadn't cut up a bunch of strut material only to have the move negated! In retrospect, whether it was working with strut material or chunks of aluminum, it was a lot of work for naught.

A day later I had the adapter brackets removed, the floats back to where they were originally, and flying again. I still wasn't cleared to land on water, but at least we had determined that the step-to-airplane position was more or less correct. Three days later, I made a decision while flying that would require the removal of the floats and a BUNCH more work than the earlier keel damage...stay tuned.

Lynn

Lynn Matteson

10-15-2015, 07:18 AM

Paul-
I should point out that the floats were originally set up with the step at 5" behind the c-of-g, so the moving back of the floats had it to about 7 3/4 inches or so.

Lynn

Clark in AZ

10-15-2015, 07:25 AM

WOW! What a story. Waiting for the next installment...

av8rps

10-15-2015, 10:48 AM

Paul-
I should point out that the floats were originally set up with the step at 5" behind the c-of-g, so the moving back of the floats had it to about 7 3/4 inches or so.

Lynn

I'm thinking if you stop posting the rest of the story here on Teamkitfox, that maybe I can work a publishing deal with you for the book rights? Then all those in suspense will HAVE TO buy the book to know the end of the story... :rolleyes:

Yeah, I was surprised that 5 inches didn't work originally. A really good test for identifying if you have the step in the best location is to step taxi at about 35 to 45 mph to see how stable it is and if it will easily porpoise , or if it will fall off the step. Properly set as on my Model 4 you can hold full forward elevator at 35 mph and only develop a mild, very gentle porpoise that is easily stopped by reducing the down elevator just a bit. So I'm glad to know the original number wasn't way off. But I guess I wasn't sure what your instructor meant about the rear of the float being snatched down on landing?

Aw hell with it....finish your story here. We can get together later to write a book (once you have yours working like they should). We'll call it "How to fly floats". Oh that's right, J. Frey has already written that one. Maybe a bit more specific like "How to fly floats, with a Kitfox attached". :cool:

Lynn Matteson

10-15-2015, 01:10 PM

Or "Flying floats with a lack of power and too many people aboard" ?

Now the big one...

Three days after I had set the plane back to its' original location relative to the floats, and flying it off the ground only, I made a spur of the moment decision to fly to Coldwater (KOEB) airport for lunch with 4 other planes. I was the last one to get there, and I had heard all the others calling for landing on 07. The wind was 150 at about 14 knots, as I recall. That made for an 80 degree crosswind landing if you took 07, or a 10 degree slight headwind if I took 16, which is turf, but crosses both 7-25 and 4-22. Thinking I'd be better off dealing with the turf-to-hard stuff transition than the 80 degree crosswing, I opted for the 16 turf runway. Making sure the wheels were down and locked, I called for the landing and eased it down, cruising over 7-25, and touching down just after that runway, and getting on the brakes hoping to get slowed before I crossed 4-22. Well, I didn't, and the transition was not as smooth as I would've liked. The plane bounced a bit, crossed 4-22 and I got slowed down and made the turn-around and taxied back to the restaurant, which is near 7-25 mid-field. Had a nice lunch of French Onion soup, swapped lies with the rest of the gang, told them of my decision process that had me coming in like I did, posed with them for pictures by my plane, and we all headed out. By this time, the wind had shifted to better favor an 07 midfield departure, and off we went. I retracted the wheels, everything seemed ok, and I flew home. Got home, called out...to myself...all the usual landing tasks, wheels down especially, and landed without incident. Taxied to the hangar, pushed it back inside and was feeling pretty smug until I noticed that the right front wheel was sitting kinda offset. The front fork had a couple of about 10 degree bends in it. It is made of two 3/16" aluminum plates, parallel to each other, but now bent like a jog in the road. The fork would still retract, but it was offset, and would require replaceing. Then I looked further into the mountings, and saw that the upper part of the bulkhead was ripped right at the flange where it was riveted to the outer skin. There are two plates that are supposed to be braces, but they both broke off during the landing, one was missing, and the other was hanging by a thread, I easily pulled it off. The welds were very poorly made (factory), not penetrating nearly enough for the job. When I get a replacement part, you can bet that I'll do a much better job of making those welds secure!

So now I've removed the floats, I'm back flying on wheels, and I have the one float home in my shop and I'm currently designing a suspension system for the front of these floats which will absorb any future landings like the one I have described. Harking back to what my CFI told me: "Make all landings on pavement whenever you have a choice, and if your destination is turf, go somewhere else for breakfast" That's a little harsh, I think, but after the landing that I made, it's probably better to have listened to him than not.

I had thought of running low pressure in the tires to help absorb shocks, but the tiny little...2.80/2.50-4's...don't carry enough air to allow for such a practice. The mains are 4.00-6's, so I can run them a bit on the soft side which will help, but making a spring suspension for the fronts is definitely the way to go, I think.

I've tried to straighten the bulkhead where it is bent, but to no avail, so I've cut the upper part of the bulkhead out and will replace it and strengthen it in the process, as well as design and build the aforementioned suspension system, using a small coil spring....at least that's the plan for now.

My home field is turf, so I'm stuck with at least one takeoff and one landing on turf, and so I have to have something that will hold up to these conditions if I'm to fly with the floats at all. Making the floats stronger and capable of handling rough field conditions through the addition of some sort of suspension system will be top priority on my calendar, for sure. Then I can get back to seeing if it will make a worthy seaplane.

Back to what you said, Paul, about the rears being snatched down....Brian says he has worked on large seaplanes...Widgeons, etc...that would demonstrate this phenomenon of "snatching". He says he felt the tails of my floats being sucked down during landing...(my ass is too old to feel anything anymore)...and he calls this being snatched down. What they did to improve this condition was to make a hole in the bottom of the area back behind the step, and run a vent tube up from there, exiting out the upper side of the float skin. This vent, he said, breaks the suction that occurs from the water passing under the step, and affecting the bottom of the rear portion of the float....I hope I'm explaining this right. He showed me a fuselage that is in one of his hangars that is a Widgeon that has this vent. It is just a box-shaped tube that connects the upper side of the float to the bottom of the float, which allows air to enter from the top and out the bottom, and supposedly breaks the vacuum in that behind-the-step area. He also said that he's never seen this on a set of floats, but has seen it and done it on hull-type floats.

Part of the reason for his feeling so strongly about this tentative modification is that the "sweet spot" is very hard to achieve....it's either on the step, or the tails are in the water when "on the step" is being sought.

He had me measure the Edo floats on the Cub, and on my floats, comparing the angle behind the step on both makes. I found that the Edo's had 0.8 degrees greater angle than the Zenith's, measured from the horizontal to the rear keel. I didn't think that less than a degree would make much of a difference in finding the sweet spot, but I could be wrong. In any event, I won't be cutting these vent holes until I repair the floats, and have weighed all the input that I can gather concerning this theory. Whatcha think?

Lynn

DesertFox4

10-15-2015, 04:03 PM

Great read Lynn. "It's not easy flying floats, the first time" might be the title of the book. I've seen this syndrome before while watching a couple friends attempt water flight. Just more to it than meets the eye.

av8rps

10-15-2015, 09:50 PM

Lynn, and everyone else following this thread,

This might take me a few posts to answer all the various things I've picked up on from Lynn's experience. And I might be all over the place with the order of how I adress things I picked up on, but here goes.

Let's start with the floats;

Zenair probably doesn't want to hear this, but I really think they should pay closer attention to not only the strengthening improvements the Czechs applied to their floats, but also to the quality of how the Czechs built their floats. A float takes a huge pounding across the water, as well as when operated off turf runways, so quality is equally important to design.

I'm sorry if I sound like I'm bashing the Zenair float, because I actually like the float (for the money). But I've looked closely at the Zenair compared to the Czech produced versions, and there is a huge difference in my opinion. Especially in the nosewheel and gear mechanism and overall construction quality. At least that's my opinion.

So with that said, and having confidence in Lynn's building abilities (have you seen his Fox? It's a beauty...), I don't think Lynn built the floats poorly. Rather he is dealing with a product that while it works in its original form, it only does so marginally. It is likely that had Lynn stayed on pavement, and did all super-nice gentle landings, he probably wouldn't have these tales to tell.

Now in defense of the Zenair float, pretty much all amphib float gear mechanisms are weak. My Aerocet amphibs on my Kitfox are probably even more delicate than the standard Zenair, so I avoid turf runways like the plague. Now if I know it is a super smooth grass strip, I may go in, but I will do everything I can to grease it on as smooth as I can while also minimizing taxi and takeoff.time. Sadly, that is generally the price to be paid for having an airplane that can land on water as well as land. Spend big bucks (35 to 55k) and you are more likely to have an amphib float that will do better on grass. But it likely will be heavier, and still not guaranteed to be any more sturdy. Again, that's the price you pay to be able to operate on land and water...

I would like to hear more from Lynn so I could adress water performance. So while I adress other things, maybe Lynn can fill us all in better regarding water performance.

On that comparison of the float angle being off compared to the Cub, while 1 degree doesn't sound like much, the best way to get an underpowered airplane off the water better (aside from more HP) is to make the wing do more of the work sooner by increasing the throat angle, or angle of incidence of the wing in relationship to the floats. Not sure if you remember, but I believe I suggested making adjustable length fuselage float attach brackets so you could easily change as needed. I think you will be amazed if you increase the throat angle by a few degrees. Downside is your cruise will be a bit slower, but you will also be able to land a bit slower with more positive wing to float incidence.

Oh, and about that vent tube for the step...other than the old Avid fibreglass float designed by Dean Wilson, I have never seen a float with a ventilated step like Grumman used on their flying boats. I also own a Lake Amphibian (4 seat production flying boat designed by two Grumman engineers) and it does not have a ventilated step. So I believe it is overkill on anything but a real heavy and fast amphib (like the Grummans) that develops a lot of speed (and suction) on the step to takeoff. I could be wrong, but I'm willing to bet if you do that to your Zenair equipped Kitfox, you won't notice any improvement. You'd probably get better results if you put anti hydrophobic paint on the bottom of your float. But hey, if it's easy to ventilate the step, go for it. Dean ventilated the step on his float with a simple horizontal hole drilled on the back side of the step, and then ran a tube into the top side of the open storage compartment. Even better would be to use a ram air scoop into the airstream that would actually pressurize air into the area behind the step, making air bubbles. But again, that is all in my opinion overkill, which is why I believe you never see it done on floats.

And for the record, I'd be amazed if ventilating the step will do anything to keep the airplane on the step, or "the sweet spot" better. That is more a function of float placement and location of the step relative to center of gravity, and the pilot getting used to the airplane when on the step. High speedwater taxiing is the best way to get the feel for that in my opinion, as when you're in takeoff mode, you're usually focused on getting it to fly. High speed step taxiing allows you to "play with it" on the water to leisurely get the best feel for it. I always step taxi a new to me airplane first before flying it, as that gives me a really good feel for the airplane before having to actually fly it. However, please note that a lot of seaplane accidents are related to high speed water taxiing. You have to gradually work your way up to that, and try to limit yourself to great water conditions with little or no waves and /or boat wakes. I have to compliment you Lynn about your comment about feeling uneasy doing step turns as that tells me you probably already have a good feel for step taxiing. Sharp turns on the step should rightfully bother anyone that has a good feel for the airplane, as the physics and inertia of that step turn are working against you, and have in fact wrecked a lot of seaplanes. So whether just on the step, or while doing a step turn, always be on top of your game. But learn it well and you will have a blast doing it. I swear I step taxi as much as I fly when wind and water conditions are good.

More later...;)

Lynn Matteson

10-18-2015, 06:18 AM

Thanks for the input, Paul. I tried to reply yesterday, and spent nearly 2 hrs thinking and typing, and while correcting something I'd written, it all went away....never to be found. So I'll respond later, but I'm heading out for a flight to get chili....and the weather is chilly!:)

Lynn

Lynn Matteson

10-19-2015, 03:34 AM

Apparenatly I need to add something up here to satisfy an error message that says I need to lengthen my message to at least 10 characters...eh???

Lynn Matteson

10-19-2015, 06:50 AM

I just had a good look at the damaged #2 bulkhead on my Zenair floats. It looks like the crack at the top of this bulkhead....it's the bulkhead that carries the entire front wheel retracting mechanism...had started way before I made my landing at Coldwater (KOEB). In looking further at that crack, it is not a new crack, but shows aging...blackness from probably being rubbed back and forth in the time prior to the hard landing at OEB. In studying this area further, it is obvious that the upper flange on this bulkhead, and the bend that forms this flange is the weak link in the front gear layout. This bend is what cracked. It is (now) obvious that this area must be reinforced, as it is this area that ultimately takes the shock of landing and of all bumps on rough surfaces. The bulkhead itself is well "armored" but there is no reinforcing at the upper flange and here is where it is weak, and subsequently failed. I can't wait to check the other float to see if it too, is cracked.

Lynn

av8rps

10-20-2015, 09:31 AM

Lynn,

I am really sorry to hear you are having so much trouble with your Zenair floats. It shouldn't have to be this difficult. I've flown those floats on different aircraft over the years, and honestly I have to say they are overall a very good performing float both on water and at the airport.

As an example I've flown a set on a Rans S7 with a 912s on it for about 30 hours, and even loaded with passengers as big as 375 lbs off the water it still did well. Here's a video of that same Rans loaded with 2 adults doing a water takeoff https://www.youtube.com/watch?v=mzHPDLfsOEI and this is their landing showing both guys in plane https://www.youtube.com/watch?v=DQJ4cPhVhFg . You will notice the takeoff run wasn't very long at all, and the water handling is indicating nothing unusual. It is a very good flying LSA amphib overall. That is the Czech built version of the Zenair float. So the design is the same, with the exception of some gear strengthening improvements. Btw, that particular Rans has been landed on grass lots of times, and as far as I know the gear is still holding up ok. And one strip it occasionally goes into is pretty rough, far rougher than I like to go into with an amphib.

For water performance of the Zenair, that same basic Zenair float design is the same on all their smaller floats, and it has been used on some super high performance floatplanes. Take John Knapp (aka Snaps) and his Zenair 750 straight float equipped Avid Flyer with a Rotax 583 2 stroke that no one at Greenville Maine's seaplane take off contest can beat. Solo he can get off the water in under 3 seconds. Here's a video showing performance https://www.youtube.com/watch?v=qjDSatUSoCY . I also have a video from OSH showing him taking a 385+ lb passenger off the water in only 10 seconds. And he was grossly underfloated, as his Zenairs were only 750 lbs of buoyancy (a more appropriately sized float would have done better). So with all that said, I don't believe the float design for water performance is poor. There are just too many cases where it has proven itself to work well.

I do agree that the stock Zenair gear could stand to be a bit stronger. But it sounds like you may have figured out how to improve that part? I also agree that it would be nice to add some suspension to the nosewheel area, as that would reduce stress on the float itself. I have always found when landing an amphib floatplane that if I can do all I can to land on the mains (tail low) and then do all I can to keep the nosewheel off until as slow as possible that I can reduce a lot of stress on the nosewheels. In my Kitfox I can keep the nosewheels off until I get into the low to mid 20 mph range. You can also do the reverse to takeoff, getting the nosewheels off as soon as possible to reduce nosewheel stress. I like to think of all operations on amphib floats like doing "soft field" operations with a tri-gear land plane.

Next installment to this thread I will address the gear position strategy I've used since 1993 when I first started flying my Lake Amphibian (which if you mistakenly land in the water with the gear down is almost always fatal... so Lake instructors drill you VERY hard on proper technique for gear position).

Later...

av8rps

10-20-2015, 12:48 PM

I just couldn't resist after stumbling on this old 1979 magazine last night...:cool:

av8rps

10-20-2015, 04:11 PM

Ok, now that I'm done screwing around I will get serious...

In 1993 when I was trained to fly my Lake Amphibian, I was taught to always say out loud my landing intention and the landing gear position at least two or three times during the landing phase. This training is critical in any amphib, but ultra critical in a Lake because most gear down water landings result in fatalities. I paid special attention to that part of my training after I saw a picture of a Lake that landed in the water gear down. Everything forward of the wing was gone - it looked as if a bomb had gone off in the cabin! (for anyone that doesn't know what a Lake Amphib is, this link will not only show you what a Lake is, but also how the gear goes up and down for land and water ops https://www.youtube.com/watch?v=2Hxh_8EEohc (https://www.youtube.com/watch?v=2Hxh_8EEohc) [see if you notice a little dog while you're at it] )

So getting back to my procedures for proper gear position, here is an example of what I do when flying my Lake Amphibian that can be applied to most any amphib;

At an airport landing on pavement, my first effort to check my gear position is when I initially enter the downwind for the landing pattern. Once I have all normal traffic duties accomplished I say out loud to myself "This is an airport landing, and the landing gear is going down" while reaching over and putting the gear handle into the down position. A few seconds later I look into the mirrors that are attached to the wing floats so I can look to see that the nose gear is actually in the down position, followed by a visual on each main gear (mains are easy to see on a Lake as they are right next to the cabin when down) and that my hydraulic pressure is up. Last, I verify the landing gear position by lightly touching the "Gear down" lights as well as the gear handle to make sure they indicate the gear is down and locked.

Then when I make my downwind to base turn, during the bank I again call out my gear position. But this time I also look into the mirror that is on the lowest wing so I can see the nosegear hanging down against the nice blue sky / horizon (much easier to see against a one color background than when the aircraft is level), while again checking my main gear visually, double checking that my hydraulic pressure is holding, then again verifying and touching my "gear down" indicator lights, and also lightly touching (but not grabbing) the gear down handle to verify its position.

Last, right after making my base to final turn, and once happy with my stabilized approach to the runway, I make a last landing gear check. Again I say out loud "This is an airport landing, and the landing gear is down", followed by one last visual check to make sure the gear is down, my hydraulic pressure is good, the gear down indicator lights are on, and the handle is down, all indicating the landing gear is in the down position and locked, ready for an airport landing.

For water landings, well before my approach to the water surface (when I still have plenty of time and space) I will call out loud "This is a water landing, the landing gear is up, I'm now a boat", while looking in my mirrors and banking to verify the nose gear position is "up" against the sky, then verifying visually the mains are up, hydraulic pressure is good, followed by a visual and touch verification of the "gear up" lights, and touching (but not grabbing) the gear handle to verify it is in the up position.

Then when I am on my final approach to the water landing, early in the approach I say one more time "This is a water landing, the gear is up, I'm now a boat", while again making a last visual check of the gear position, hydraulic pressure, and the gear up indicator lights, along with the gear handle.

As a personal rule, I always verify gear position before any landing. Even if I just took off from the water and plan to do a landing right after takeoff (also known as a "splash and dash"). Most seaplanes do not have an "Uplock" on their gear mechanism, so just imagine what might happen if on that last bouce off a wave that made you airborn, the gear unlocked for some odd reason? (... a hydraulic line that came undone, a gear link broke, etc.) You'd unknowingly splash down right after your takeoff with the gear down, spoiling a lot more than just your day!

So even though the Lake Amphib has a really nice uplock in its gear design, and so do my Aerocet floats on my Kitfox, what if for some reason or other it stopped working that day? Plus, because I often am flying other amphibs, I just make it a point to never assume the gear stayed up just because I thought it should. So again, I verify visually the actual gear position, even for splash and dashes.

Also, if you have a passenger with you don't be afraid to task them with making sure you are doing the right thing with the gear. I've found they like to know about that when explained to them, and that they like to help you keep an eye on it too (self preservation is a really strong instict apparently ;)). Just include it in your passenger pre-flight seaplane safety briefing (which you should always be doing anyhow).

And as far as using lights and hydraulic pressure, that is fine. But more importantly is actual visual verification of the landing gear position. My Kitfox amphib only has mirrors, no lights, and no hydraulics, being that it is a manual system operated mechanically by a Johnson bar. So I rely entirely on my mirrors. Many would say the Johnson bar is all you need, but what if a cable or a pulley inside the float that actuates the gear broke? My handle would show the gear up, but part of it could be down. So again, I trust my mirrors to visually show me where exactly my wheels are before any landing. Indicator lights and switches are prone to failing in a water environment, so I only consider them an additional, or backup to visually verifying gear position. The same goes for voice warning systems. They are only as good as the switches that actuate the gear lights - which is poor at best in my opinion.

Call me old fashioned, but I prefer to trust my eyes for knowing exactly where the gear is when flying an amphib. And if it just wasn't possible to do it effectively with mirrors, you'd be seeing me installing a small camera and video screen system in my plane so I could use that to visually verify my gear. They can be had for under a hundred bucks these days, and could be used for some cool seaplane video stuff as well (like this https://www.youtube.com/watch?v=j3kO2nZoSDA ). In fact I have thought about doing a camera system for a few years now, after installing a cheap backup camera on a camper a while ago and seeing how well it worked. But for now my mirrors still do a good job, so I'll keep what I have. But my next amphib (a new Highlander) will definitely incorporate mirrors AND a camera system.

Ok enough rambling. I sure hope those of you that hope to one day fly floats don't get discouraged by all this discussion about issues related to amphibs. Once you get your plane set up properly, and you get the proper training and get used to your new amphib, you will have an absolute blast being able to fly from land to water and back. It's like having your own magic carpet. I've always said that amphib floats is the best accessory you can add to an airplane. It in fact will make your airplane an amazing machine that will take you to places you probably otherwise would never experience. So don't let any of this discourage you. I can't imagine not being able to fly my Kitfox off water...it works so well.

Lynn knew going into this that turning a Jabiru powered Kitfox Speedster into an amphib might be a really challenging task. We had talked previously. And it certainly has been from all he describes. I'm almost embarassed how easy mine was to make work after reading of his struggles. But I have to say that it still looks like Lynn is going to pull off what many of us wouldn't believe was even possible with the Jabiru powerplant. So more power to him (no pun intended...really). I'm confident he is close to success, and will one day soon succeed in his mission. It might even be a bit selfish on my part, but I have this vision that one day soon I will see him land at the EAA Oshkosh Seaplane Base in his cool Kitfox amphib, and will have the time of his life in his new adventure machine :)

DesertFox4

10-20-2015, 11:09 PM

I feel as though I could almost take my seaplane check ride after following this thread. :) Thanks for all the good reading guys. Something about float flying appeals to me like no other kind of aviation even though I have only some experience as a passenger and zero time on the controls of a web-footed aircraft.

Now , back to more float talk.;)

av8rps

10-21-2015, 08:51 AM

A checkride?? That's funny!

I'm at least glad to know people are enjoying the thread while also learning from it.

I am a little concerned however that in trying to explain all this seaplane stuff in detail that it might appear a bit overwhelming to the average guy that is thinking about one day flying his or her Kitfox as an amphib. It's not really anywhere near as hard as this thread is making it appear. Not only does a Kitfox make for an excellent seaplane, but pretty much anyone can learn to fly an amphib well, and even though it may appear complex and overwhelming, if one learns properly and then practices it regularly, it will become second nature. And if one does it that way, it also can be done safely.

I think it is a lot like the latest trend of booney bashing with big tires and STOL aircraft flying around on sandbars and landing on tops of mountains (oh, and not to forget skimming water with your tires :eek: ). Doing that kind of flying certainly requires one to develop special skills, and an extreme ability to exercise good judgment and common sense, knowing what you and your airplane are realistically capable of.

But just like flying an amphib, when you get that all figured out just look at all the cool places you can go that the average guy with his 180 mph Spam Can can never go. I personally enjoy booney bashing almost as much as flying off water, as both require special skills that in my opinion not only makes flying more interesting and enjoyable, but the additional challenges also makes you a better pilot.

So we can beat this to death some more if there is further interest, or if people have additional questions. Otherwise I think we probably need to just let Lynn work on his floats so he can report back this spring after trying out his modifications.

Paul

av8rps

10-21-2015, 11:19 AM

Lynn,

I know you are a very creative and talented guy. So I just want to plant a seed with you that might make the biggest difference ever with your Kitfox.

Think about the possibility of putting some sort of a prop reduction unit on that Jabiru so you can spin a longer, larger prop. I am absolutely convinced that if that were done to the Jabiru that it would truly be a kick-ass motor for a STOL type airplane like a Kitfox. Yeah, I know it would add weight, and it might require a bigger effort than it sounds. But I'm convinced it would produce so much more thrust that you wouldn't even notice the extra 10 or 20 lbs for a PSRU. And you'd be very happy with the extra effort to do it.

I say all that because of knowing how well my 80 hp 912ul with a gearbox reducing the prop speed works on my Kitfox IV amphib. I do cheat a bit by having an IFA IVO prop, but even if I use a fixed pitch prop setting it performs really well. As an example, the other day I was cruising around (on floats) at 105 mph at approximately 5000 rpm, which is only about 70% power with the prop setting I was using. While we probably can attribute most of that to the efficiency and performance of a 912 matched to a really good airframe, the reality is that turning a prop at a very efficient speed produces the most thrust for the available horsepower or torque. That in my opinion is where a 912 Rotax prevails over most other engines in its weight class. Turning a small and lightweight engine at high rpms so it can make the most horsepower and torque out of its size, coupled to a gear reduction that makes the propellor most efficient is why I believe the 912 does so well.

So with that said, now compare your Jabiru to the 912 ul. It is approximately the same weight as the 912ul (actually lighter), and produces about 4 hp more, with similar torque, but at much lower rpm. But then consider engine displacement. The 912ul is only 1,211 cc, or 74 cubic inches. By comparison the Jabiru is nearly 1,000 cc's more than the 912ul, with a displacement of 2,200 cc, or 134 cubic inches. So in a nutshell, the Jabiru actually has the same or more power than the 912ul (and probably way more potential for more due to more available displacement), but just doesn't apply that power to a prop as effectively or efficiently as the 912.

So imagine if you could add a prop speed reduction unit to the Jabiru that would allow it to turn a propellor at similar speeds to what the 912 does? I personally believe you would actually have as much or more power than the 912 ul.

To support my reason for feeling a PSRU would do so much for a Jabiru Kitfox, I will share a story most here probably don't know about our airplanes;

I remember Dean Wilson (designer of our airplanes for those that don't know) telling me about the first flights of the Avid Flyer prototype being a huge disappointment. It was powered with the most popular ultralight aircraft engine at the time, a Cuyuna 43 hp two stroke engine with a standard 50'ish inch ultralight prop bolted right to the crankshaft. Even though Deans calculations said 43 hp should be more than plenty HP for the very lightweight 364 lb Avid Flyer prototype, test flights returned poor at best performance numbers. Climb rate was only 200 fpm, and cruise only 55 mph. Frustrated, Dean almost scrapped the whole idea of the Avid Flyer. But after thinking about it more, even though the entire ultralight industry was using that engine and prop combination on most every ultralight, he came to the conclusion that turning that short prop at the rpm of that Cuyuna (about 6500 WOT) was making for a very inefficient propellor, resulting in very little thrust for the available horsepower.

So Dean went down to a local junkyard and bought the planetary drive out of a Ford C3 transmission. Then he machined a gearbox housing that held the ring gear and sun gears in place, and a adapter that would bolt all that to the crankshaft of the Cuyuna. Now he had himself a 43 hp Cuyuna that would spin a 6 ft diameter propellor with 36 inches of pitch at only 2200 rpm!

The test flight that followed the gearbox addition produced amazing results from the little 64 lb, 43 hp Cuyuna;

Instead of 200 fpm climb, he now had a 1,460 fpm climb rate!

And cruise jumped from 55 mph to 80 mph!

So every Avid Flyer kit was sold with a PSRU installed on the Cuyuna. And shortly after that (about the time Kitfox started), Rotax showed up on the light aircraft scene with their PSRU equipped 2 stroke aircraft engines. Of course we all know where that all went, with Rotax now being the number one aircraft engine manufacturer in the world (I often wonder if they ever gave Dean Wilson any credit for any of that, as they should have IMHO ...)

So, imagine discovering the true capabilities of the Jabiru engines by adding a gearbox that allows for a larger, more efficient prop, just like Dean Wilson did with the Cuyuna? I could be wrong, but I'm willing to bet you would see an amazing difference in your Jabiru Kitfox with the addition of a PSRU. And it would improve in all operational modes, climb and cruise, and land or sea, .

There you go Lynn...there's the seed I wanted to plant :)

Dusty

10-21-2015, 11:51 AM

At risk of getting a little off topic,
I would agree the jabaru with a reduction would be a serious contender for one of the best power plants around.
Cooling would need to be improved(Rotec water cooled heads?)and a possible shift of the torque/power curve.
If the weight worked out ok, this would be worth considering for our type of aircraft.
Still some big boots to fill,the 912 will be top dog for a long time!

av8rps

10-21-2015, 03:09 PM

Yeah, we probably should move this Jabiru PSRU to a thread of its own as there might be more interest in it where it is more obvious. But for now I guess we are still relating to float flying, so unless the moderators want to copy off this part and start a new thread, we can continue on here.

I'm somewhat aware of those liquid cooled heads from a friend that suffered at length with cooling problems with his early Jabiru 2200. But it seems that Lynn has figured a lot of cooling issues out with his Jab powered Kitfox, so I'm thinking it is possible his engine with a PSRU might actually run cooler?

Think about it, if it works like I think it might, he will immediately see more air through his cowl merely for the fact that the airplane is very likely to gain cruise speed with the same power setting. Plus, the bigger prop will probably push more air through the cowl too. I believe right now he is using his Jabiru engine to its max potential, just that the short prop isn't efficient on this airframe. So with a more efficient, longer prop he might not need to run it as hard as he does now. So again, that's why I think it could actually run cooler. I forgot to mention earlier that when Dean geared the Cuyuna on the first Avid, he saw lower temps from better cooling. Not sure all the reasons, or if the fan cooled Cuyuna would compare to the free air Jabiru that way? But maybe?

You bring up some very good points about doing this, and certainly all worth considering. But I don't think any of us will ever truly know until someone tries it.

I agree it would be a really big deal if a PSRU equipped Jabiru could even get close to what the 912 does, as the 912 is certainly the proven leader in applications like ours. But just imagine the response if it did better? Hey, maybe our Rotax prices might then finally come down ;)

HighWing

10-21-2015, 09:35 PM

I'm at least glad to know people are enjoying the thread while also learning from it.

Paul

I for another am enjoying it. I once flew in the factory float equipped Series 6 and that likely is it for me, but reading a very knowledgeable conversation between two of my favorite List contributors over the years brings back great memories along with a treasure trove of new knowledge.

Landing at Cameron Park after a "Splash and Dash" at Folsom Lake

9991

One of these guys was my pilot, do you recognize the guy on the left?

9992

Lynn Matteson

10-22-2015, 12:44 PM

Paul, Lowell, Dusty and others-
Thanks for all the valuable insight and ideas regarding my float installation/training.
Paul, I just found the diagram that I drew after I had the floats rigged. I checked float top, lower door sill, and wing angles with a digital level. My drawing shows the floats at 2° up, the door sill at 6.2° up, and the wing at 8.1° up. Now on the wing, I checked the level figuring the center of the leading edge and the center of the trailing edge (I used a block at the rear to achieve a straight line reference through the "center" of the wing). So from what I'm seeing, I have 4.2° of incidence, right?....top of float to datum of aircraft. Then perhaps 1.9° more throat angle, for a total of 6.1°? I'm heading for the hangar right now to recheck the datum-to-wing angle. I will get reading this time using just the bottom of the wing and forget the "theoretical center of the wing" for now. I can't check the float-to-fuse angle as the floats are off. I'll try opening up the throat angle when I install the floats after repairs are made, but it seems as though as slow as it flies (with floats on), I gotta have more than enough incidence, eh?:rolleyes:

Lynn

Lynn Matteson

10-22-2015, 03:46 PM

av8rps

10-23-2015, 12:44 PM

Interesting info Lynn. I will dig out my digital protractor this weekend and measure mine to see how it compares.

A 5 second land takeoff is pretty good in my opinion. That's why I said I believe you have most of the Jabiru figured out. But I still believe it can make a lot more prop thrust with a longer blade, if there was just a way to run a longer one.

Even with my 912 that is evident, as my Kitfox on floats gets off a lot better with the longer 72 inch 3 blade than it does with the 68 inch 3 blade. But the smaller 68 inch prop makes it fly faster by probably 5 mph. My Lake amphib is much the same; I tried a later model Lake prop on my airplane once because I was told it would fly a lot better, and it did. I gained almost 200 fpm and about 10 mph, yet both Hartzel 2 blade Constant Speed props looked essentially the same. The only significant difference was that the later model prop was 74 inch diameter rather than the older prop that was 72 inches. Two inches more prop diameter did amazing things for the Lake. So I have proved to myself again and again that the longer diameter props make more thrust.

I don't meant to beat a dead horse on this subject, especially knowing that you get pretty good performance from your airplane in its current state. But bolting floats onto an airplane does tend to bring out the worse in an engine, prop, airframe combination. So even though you are getting good performance on wheels as it is, I still believe your engine probably has a lot more potential to make more power with a more efficient prop speed.

av8rps

10-27-2015, 03:45 PM

Holy crap, Batman....I just put the digital level on the door sill and the bottom of the wing...the door sill read 11.8°, and the wing bottom (straightedge along the bottom surface of the wing) read 10.5!! I also re-measured the chord line angle (using the point on the leading edge that gives the chord its' maximum length) and this reading was 12.8°. Now I'm confused....if the bottom of the wing is compared to the door sill, the incidence is negative 1.3°, but if the chord line is compared to the door sill, the incidence is 1° positive. And from my previous post, I said that the float-top to door sill angle was 4.2°, and with hardly ANY "built-in" incidence, it doesn't sound like I have nearly enough throat angle....no wonder this thing won't get off the water!

Incidentally, I took a flight while I was at the hangar and it took 5 seconds to get airborn...not a worlds' record by any stretch, but seems like I have enough power to get the bird up without floats.

Lynn

Lynn,

I went to the airport today and measured the difference between the bottom of the door frame and the top of my Aerocet float - on my Model IV that door frame sits 1.5 degrees higher (or tail low) than the float top.

But that is not the throat angle from the wing to the top of the float.

Unless we all agreed to doing a wing to fuselage incidence reading EXACTLY the same way, it is unlikely we will get readings that would accurately compare. And frankly, I don't think that number matters when we have a known good flying Kitfox amphib (my Model IV) that has a fuselage exactly the same as yours to compare lower door frame measurement to the top of the float measurement. I'm not trying to minimize anyones in depth float rigging analysis, or their math. I just think it is best to follow an example that is known to work well.

The only real variable between our two very similar airplanes would be the angle in the step area on the bottom of each of our floats. Yes that could be off slightly, but it would just be diffence in the float design, and I'd be willing to bet it is minimal. And I'm sure if we compared other brands we'd find them much the same as the Aerocet or the Zenair, but likely still slightly different. (Hopefully my explanation here makes sense...)

Another thing that might help you is a recent discussion over on the Highlander / Just Aircraft forum where I have been trying to help a couple Highlander guys rig their Zenair 1450 amphibs to 912s powered Highlanders. The most recent post is interesting to say the least, as one builder just put his floats on the way Zenair said to install them on a Zenair 750 (which is something I would have never suggested as a Highlander is very different aircraft in design from a 750), but from what I can tell he hit the jackpot!

Ironically, most of his final rigging numbers were in line with what I had originally suggested to another Highlander builder, but he did locate his step differently from what I can tell in his explanation. I'm not 100% sure he said that right, but if he did then that part I find quite interesting and will probably look more into that myself. So I'm going to ask him to explain that further.

But whatever he did works very well, and he has youtube videos to prove it. I was pretty impressed with the videos, as it looks to be rigged perfectly to me (especially when he's operating from glassy water with a lot of suction issues). The only unknown would be if he might later learn of issues associated with extreme CG loading fore or aft, or something else that would be odd. Other than that, the videos show it flying on and off the water near perfectly. In my opinion, at first glance I think he nailed the rigging setup! In fact, I'm keeping his numbers and the next time I install my Highlander floats I'm going to compare my numbers against his. Maybe he has better numbers than me? If so I'm not ashamed to admit there may be a better way to do it. I'm not too proud to modify my rigging if my airplane will perform better ;)

Here's the link to that forum subject; http://wingsforum.com/viewtopic.php?f=218&t=23589&start=15
The last post has the info most valuable to your install.

And here's the separate link for the takeoff video; https://www.youtube.com/watch?v=TPDpMSkokHY&feature=youtu.be

And here's the landing video; https://www.youtube.com/watch?v=HEaz1l7QweI&feature=youtu.be

If your numbers are close to what he is doing, at least you'll be vindicated for your setup. And if not, maybe that can be the information you need?

For me, seeing is believing. So his videos are priceless to guys like us that are trying to set up a float plane for best performance.

Lynn Matteson

11-16-2015, 06:50 AM

Thanks for the info, Paul, and sorry it took me so long to get back here to the forum...too many irons in the fire!
Yes, I agree that we all need to "standardize" the method of measuring/comparing angles, etc. when we discuss these matters. And in the matter of comparing our VERY similar (read: identical) airframes, the door bottom-to-float top is the one that should be used. As far as the angle of the step area on my floats is concerned, the top of the float is parallel to the bottom of the keel/skin for about the last 24" or so, so I doubt that that is very different between our set-ups. So at this point, I'll forget about the wing incident-to-float top comparison, and stick to the door frame bottom-to-float top comparison, and most likely increase that angle a bit when I reinstall the floats the next time....spring most likely.

I've been thinking lately that the most likely problem for this beast taking so long to lift off is the added weight of my CFI, (along with the short prop, low power, direct drive Jabiru power) which is about 235 lbs. If I could get my training revved up a bit in his Cub, and get his approval to cut me loose and fly the Kitox alone, I think the whole frustrating matter would be a thing of the past.

Again, thanks for all your help, Paul and others, and I hope that this thread hasn't scared off potential float flyers...my situation is kind of unique, I'm thinking.

Lynn

av8rps

11-16-2015, 02:21 PM

Hi Lynn,

Knowing how busy you always are, I figured you were just off on projects.

Yes, I agree that adding a bit more wing to float incidence will help your situation. Most would probably do that with my Kitfox, as it is pretty much the least amount I would ever put on a floatplane. But I like it the way it is. I'm certain however if I increased my throat angle on my Kitfox, I would shorten my takeoff run quite a bit. So in effect, my numbers are probably not the best to follow.

I think your idea of getting your time in the Cub would be a good one. Let's face it, most of these little airplanes fly best with just one person in it. The only thing I'd suggest is to incorporate your amphib ops training into your training program, even though the Cub is not an amphib. Just pretend it is so you develop habits that include proper gear position.

On that subject, I just read an article in digital Kitplanes talking about flying a Searey amphib,and the author explained Searey's new gear position warning indicator, and I really liked what they did. Granted I am really old school, so I will probably never go out of my way to actually buy one, but if I did I think I'd use theirs. I think they have it figured out.

I too hope people aren't discouraged by any of this float discussion, as yes, you are trying to do something that as far as I know has never successfully been done before (a Speedster Jabiru 2200 Kitfox amphib). And frankly, I'm impressed with what you have accomplished thus far. I think with more angle, along with those wing extensions (which will also be much more effective with the increased angle) that you will probably be happy with your new amphib. Especially if you can limit additional weight in the cabin.

Lynn Matteson

11-18-2015, 06:54 AM

Regarding my on-again, off-again training in the Cub, my instructor has me call out all the moves for landing as if we were in the Kitfox....that is: "wheels going up for water landing, pressure building ....mechanical indicators show all four wheels are up, and hydraulic pressure is maxed out on the gauges, mixture set (I've got a Rotec throttle body injector on the engine), flaps set, throttle back, etc, etc." He has me do this in the Cub even having to pretend that I'm looking at gauges...it really IS good practice.

I ordered a new front fork to replace the damaged one, and while talking to Michael at Zenair, I mentioned that I broke the top ot the bulkhead near where the rigid end of the hydraulic cylinder mounts, then told him that this is a very weak area in their design, and that they ought to strengthen that area. He said that the people who buy their floats are very weight conscious....geez, what would it cost to reinforce that area? one pound per float would be a high figure, I'm thinking. The main wheels are built adequately, as far as I can see, but those fronts are weak right at the top of the bulkhead, where the flange is formed, and this is where the stress is concentrated.

When I was building my floats, I was narrow-minded enough to just follow the instructions and build accordingly. I DID do some modifications to the main wheel amphib apparatus, but never really looked at the front wheel mechanism with an eye toward how it worked and how the design put such a huge load on a very small area, to wit, the formed top of the #2 bulkhead. It would have been such an easy matter to have reinforced that area, and spread the load out over a larger area. Well, I forgot to put my "engineer's hat" on while building them, but you can bet that it'll be on while I'm RE-building them, and mabe even use a chinstrap to insure that it doesn't blow off!;)

Lynn

N213RV

11-19-2015, 07:38 AM

Hi Lynn,

I am building a set of 1450A's right now at 26W. I sent you an email a few weeks back regarding lessons learned from your build. I will look at the above mentioned areas, but would love to get together with you soon to get some advice from you. I can either meet you at your hangar or you can fly to 26W if you are out and about. I am on vacation all next week (Thanksgiving) except for Tuesday I have to work. I can work around your schedule. Thoughts?

Thanks

Lynn Matteson

11-19-2015, 09:28 AM

Hi Mike-
I'd be glad to see you and your floats. I have your number in my cell phone, and I'll get ahold of you next week to set up a visit. If the wind ever stops around here, I'll fly over there.

By the way, I just had a flash of brilliance about how to strengthen the "problem" area in the 1150 floats, and it'll probably work on the 1450, but not sure.

To people who may be following this thread, my #2 bulkhead gave way at the top, where it is bent to form the mounting flange. In looking at the crack, it is apparent that the metal there has been "working" for some time. My idea uses a different way to mount the "fixed" end of the hydraulic cylinder. I'm thinking this method out at the present. As it is, Zenair reinforces the hell out of the back face of the bulkhead, but all this "armor" is riveted JUST to the bulkhead, and the weak point is the bend that forms the flange, and that bulkhead is only 0.025" aluminum. The reinforcing doubler is also 0.025", and another piece of 0.090" sheet is riveted to that, making the reinforcing parts 0.115" thick. But this 0.115" "thickener" is riveted to the 0.025" bulkhead such that any force applied to the rigid end of the hydraulic cylinder (read: front wheels working up and down along runway/turf) is not braced by the whole 0.140" thick sandwich ( 0.025 bulkhead, 0.025 doubler, 0.090 reinforcing material) but only by the thin 0.025" bulkhead itself. I equate this scenerio to having a wall made of 1/4" plywood (the bulkhead) with no studs, then attaching a slightly smaller in size 3/4" plywood "reinforcement" to that, then having an offensive lineman smashing into the wall....eventually the 1/4" plywood bulkhead gives way. My idea would have the wall tied into the ceiling, so that any force against the wall is spread along the ceiling.

Lynn